Here is a lovely striated and faceted clast that we encountered while on our 3-day glacial geomorphology project at field camp.
You can see that this clast was clearly worked by glacial action. The tiny striations are all carved into the rock by grinding against other smaller pieces of rock with in the glacier. Also, the rock has a really nice square shape to it, with faceted faces. This rock is nearly square as a brick, and shows all the signs of glacial sculpting.
Here is a quick annotation I drew to highlight the flat faceted faces and striations.